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May 14, 1963
PYROLYSIS
3,089,889
T. H. CLEVELAND ETAL
PRODUCTS 0F DIMETHYL HYDROGEN PHOSPHITE
AND METHOD 0F PRODUCING SAME
Filed July 3, 1950
DMl/P
@.1
'
INVENTORS
Tilo/wis ff. c¿ ¿naß/vo ,
nrraR/vgy
Èâgg
iißëgßhg
@ciotat
Patented May i4, 1%63
2
l
ducing pyrolysis products, which comprises continuously
feeding dimethyl hydrogen phosphite into a reaction zone
containing a cyclically circulating stream of pyrolyzed
dimethyl hydrogen phosphite, heating said stream to a
temperature of about 200° C. to about 300° C. to eiiect
pyrolysis of the incoming feed and continuously with
drawing the resulting liquid pyrolysis product at a rate
3,089,889
PYROLYSIS PRGBUCTS 0F DEMETHYL HYDE@
GEN I'HQSPHITE AND METHUD ÜF PRÜDUC
ING SAME
Thomas H. Cleveland, David H. Chadwick, and Edgar> E.
Hardy, Anniston, Ala., assignors to Monsanto Chemie-ai
Company, St. Louis, Mo., a corporation or" Deiaware
Filed July 3, 1950, Ser. No. 172,388
so correlated with the dimethyl hydrogen phosphite feed
as to maintain the reaction volume substantially con
10 stant. ln the practice of the above method, two products
are obtained, namely, a relatively small amount of a
The present invention relates to the products obtained
6 Claims. (Cl. 26h-Liet)
gaseous byproduct containing unreacted dimethyl hy
drogen phosphite, dimethyl methane phosphonate, di
by the pyrolysis of dimethyl hydrogen phosphite and to
a novel method of making same.
methyl ether, phosphine and inert gases and a relatively
large amount of a series of liquid products which fall
within the following specifications depending upon reac
tion condi-tions.
\An object of the invention is to provide an economi
cally and commercially feasible method of producing
pyrolysis products of dimethyl hydrogen phosphite.
Another object of the invention is to provide a method
of producing pyrolysis products of dimethyl hydrogen
phosphite with a higher overall vcontent of organic com
pounds having a carbon to phosphorus bond than is
obtainable by prior methods.
Another object of the invention is to provide a com
Percent by weight
Total phosphorus content _______________ __
32-35
0-0.65
20 Trivalent phosphorus content ____________ __
Hydrolyzable phosphorus content ________ __
4.1-7.0
Available phosphorus content ____________ __ 762-885
Viscosity in centistokes at 125° C ________ __ 52.0-10l
mercially practical method of producing dimethyl meth
The gaseous product, on cooling, yields a condensation
ane phosphonate.
A further object is to provide a continuous vapor 25 product consisting essentially of unreacted dimethyl hy
drogen phosphite and dimethyl methane phosphonate
phase method of producing the above products.
Other objects and advantages will be `apparent to those
skilled in the art as the description of the invention pro
ceeds.
The pyrolysis products of dimethyl hydrogen phosphite
and a gaseous residue including phosphine, dimethyl
ether, methyl alcohol and inert gases, which is exhausted
30
are useful as intermediates in the production of insecti
cides, methyldichlorophosphine oxide, methyldifluoro
to a burning flare.
The dimethyl methane phosphonate content of the
condensed pyrolysis product and the available phos
phorus content of the liquid pyrolysis products repre
sent that portion of total reaction product which is avail
-phine oxide and warfare chemicals. Heretofore, they
have been produced in a liquid phase reaction by' heat 35 able for use as an intermediate in the production of
methyldichlorophosphine oxide, methyldiñuorophos
ing the above compound to a temperature within the
phine oxide and related products. In contrast thereto,
range of 200° C. to 300° C. and preferably within the
the trivalent and hydrolyzable phosphorus contents rep
range of about 235° C. to 265° C.
resent phosphorus compounds `which are not available for
The composition of the above pyrolysis products is
the above use. Thus, it can be seen that a substantial
quite complex and their utility in the above applications
amount of phosphorus is lost in the formation of useless
is dependent upon their available phosphorus content
biproducts and that the avoidance or minimization of this
as distinguished from their trivalent and hydrolyzable
result is highly desirable.
phosphorus contents.
lt is, therefore, the primary object of the instant in
The “available phosphorus” is determined by analyz
ing the crude products for their total, trivalent and hy 45 vention to provide a method of achieving the foregoing
objective and thereby substantially increasing the overall
drolyzable contents and substituting them in the follow
yield of available phosphorus `over that obtainable by the
ing equation:
method disclosed and claimed in the above application.
Available phosphorus
dTotal P- ( Trivalent P-l-Hydrolyzable P)>< 100
__
Total P
The available phosphorus designates that portion of
the reaction products corresponding to the organic com
pounds having a vcarbon to phosphorus bond> and also
that part of the total phosphorus content which is avail
As indicated earlier herein, it is also an object of the in
50 vention to provide an economically and commercially
feasibie method of continuously producing dimethyl meth
ane phosphonate.
To the accomplishment of the foregoing and related
ends, the invention comprises the features hereinafter
55 disclosed and particularly pointed out in the claims and
able for use as an intermediate in the production of the
the following description sets forth' in detail one of the
above products.
As the expression indicates, the total phosphorus `con
be applied.
various forms in which the principle ofthe invention may
Iny accordance with the instant invention, dimethyl
tent is the total percentage by weight of phosphorus with
out regard to the form in which the corresponding com
60
hydrogen phosphite (DMHP) is subjected to pyrolysis
valent phosphorus is a measure of unreacted dimethyl
by heating same in the vapor phase to a temperature in
the range of about 200° C. to 400° C. to form', as a
quantitatively precipitated with molybdate.
reactor.
vention, there» is disclosed and claimed a method of pro
the uncondensed gases being exhausted to a :burning flare.
pound exists in the complex pyrolysis mixture. The tri
principal product, a vaporized mixture containing> di
hydrogen phosphite in the reaction product. The hy
methyl methane phosphonate, unreacted dimethyl hydro
drolyzable phosphorus is that portion of the total phos
phorus content corresponding to pyrophosphoric acid 65 gen phosphite, dimethyl ether, methyl alcohol and phos
phine and, as a byproduct, a complex pyrolysis product
and its esters, which may be hydrolyzed in the presence
which is condensed and collected at the bottom of the
of boiling hydrochloric acid to phosphoric acid and then
The vaporized product is cooled to condense a crude
In Vapplication Serial Number 142,737, filed. February
7, 1950, in the name of Edgar E. Hardy, which .applica 70 liquid mixture consisting essentially of dimethyl methane
phosphonate and unreacted dimethyl hydrogen phosphite,
tion is assigned to the same assignee as the present in
3,089,889
4
ò
The liquid condensate is then distilled to vapon‘ze the
of the instant invention.
unreacted material, leaving substantially pure dimethyl
The open end of the tube
13 permits the liquid byproduct to flow continuously into
methane phosphonate as a residue.
a receiver 15 as rapidly as it is formed.
The products of the above pyrolysis reaction are both
suitable for >the uses mentioned in the above application.
Moreover, the overall yield of available phosphorus
from these two products is higher than that obtainable
by the method of the above application since the
The top of the reactor 11 is provided with a take
otî line 16 for conveying the vaporized reaction product
to a condenser 17 which is cooled by water or another
suitable cooling medium. In the condenser, the vapor
ized reaction product is separated into a crude liquid prod
pyrolysis reaction has been shifted in the direction of
uct containing dimethyl methane phosphonate and un
greatly increased yields of dimethyl methane phosphonate. 10 reacted dimethyl hydrogen phosphite and a gaseous prod
Furthermore, the shifting of the reaction in this direc
uct including phosphine, methyl alcohol and methyl
tion provides an additional advantage in that the prin
ether. >The liquid product is discharged from the con
cipal product may be chlorinated more readily and by
denser by line 18 and then led into a condensate re
a greater number of chlorinating agents than the priu
ceiver 20 by line 19. The gaseous product is conveyed
cipal product of the method of the above application. 15 from the condenser by line 18 and exhausted to a burn
The following equations are believed to represent the
ing flare (not shown) by olf-gas vent line 21 or it may
reactions which take place during the vapor phase py
be conducted to a suitable system (not shown) for treat
rolysis of dimethyl hydrogen phosphite:
o
omo
011.-i|>-0H
o
ment to render same innocuous.
o
The condensate is withdrawn from receiver 20 by
o
\il--GH3 -> oHi-iL-o-rL-CHH-onßon
dm/
the unreacted dimethyl hydrogen phosphite is removed
¿n dem
ii/O@\ii
on??
20 line 22 and introduced into a continuous still 23 where
ii
P-cHt __»
by distillation at a temperature of about 56° to 80° C.
while under an absolute pressure of from about 11 to
25 of Hg, thus leaving a residue of substantially pure di
n
om-P-o~P-on3+n2o
den, H300
oon@
25 methyl methane phosphonate which is drawn off by
line 24 into a suitable receiver 25. If a product of
'
higher purity is desired, the residue may be subjected
ons
to a further distillation to recover a distillate corre
o
sponding to practically 100% dimethyl methane phos
cm--ii--o-il-OHSJr chron ___,
00H3
30
The unreacted dimethyl hydrogen phosphite is con
on,
o
o
oon;
ona-iIß-OH + ons-«ia
ona-ii/
3. The recycled dimethyl hydrogen phosphite is mixed
returned to the reactor for further conversion to di
o
methyl methane phosphonate and liquid pyrolysis prod
0cm
+ onzorr --» cHt-ii/
oon,
ducted by line 26 to a condenser 27 where it is con
densed and then recycled by line 28 to the feed tank
oon. 35 with fresh reactant in the above feed tank and then
oon,
o on
phonate.
+H2o
oom
ucts in the manner hereinbefore described.
In the practice of the invention in the above sys
40 tem, dimethyl hydrogen phosphite is preheated to its
However, it is to be understood that in view of the
boiling point and continuously introduced as a vapor
complexity of the reactions involved, applicants are not
into the reactor which is maintained at a temperature
bound by the above disclosure, since it may ultimately
within the range of 200° C. to 400° C. Upon entering
turn out that the reactions resulting in the formation
the reactor, the above compound is continuously py
of dimethyl methane phosphonate are quite different.
rolyzed to form a vaporous mixture including dimethyl
For a more complete understanding of the present 45 methane phosphonate, dimethyl ether, methyl alcohol,
invention, reference is made to the accompanying draw
phosphine and unreacted dimethyl hydrogen phosphite.
ing which shows in conventional side elevation one par
In addition, a complex pyrolysis byproduct is continu
ticular embodiment of the invention. However, it
ously produced and collected as condensate in the bot
should be understood that modifications and variations
tom of the reactor, from which it flows continuously
in the equipment apparent to those skilled in the art 50 into the byproduct receiver.
may be made as desired without departing from the
The vaporous mixture is continuously conducted to
spirit of the invention.
the condenser where a crude mixture of dimethyl meth
Referring to the drawing, reference character 1 rep
ane phosphonate and unreacted dimethyl hydrogen phos
resents a storage tank for dimethyl hydrogen phosphite,
phite is continuously separated by condensation.
the reactant employed in the manufacture of the py
The condensate is continuously introduced into a still
rolysis products of the instant invention. The dimethyl
wherein it is heated to a temperature of about 56° C. to
hydrogen phosphite is conducted by line 2 to a feed
about 80° C. while under a pressure of about 1l to 25
tank 3, from which it is withdrawn by line 4 and forced
mm. of mercury. In this operation the unreacted di
by pump 5 through line 6, rotameter 7 and line 8 into
methyl hydrogen phosphite is continuously separated
preheater 9. In the preheater 9, the above reactant is 60 from the dimethyl methane phosphonate by fractional
heated to its boiling point and then conveyed as a vapor
by line 10 into a tower reactor 11.
The tower reactor 11 consists of a simple glass or
distillation, the latter compound being continuously with
drawn in a substantially pure form into the product re
ceiver.
Upon redistillation, dimethyl methane phos
Hastelloy tube of any convenient diameter which may
phonate of the following purity is obtained:
or may not be ñlled with packing such as rings made 65
of the foregoing materials. The reactor is provided
Theory tor
with a jacket 12, through which a heat exchanging fluid
Found,
Dimethyl
percent
by
Methane
is passed in order to heat the dimethyl hydrogen phos
weight Phosphonate,
percent by
phite up to reaction temperature, that is, to a tempera
70
weight
ture in the range of 200° C. to 400° C.
The bottom of the reactor 11 is equipped with a Z
shaped tube 13 iilled with a liquid 14 which serves as a
liquid seal. This liquid consists of liquid pyrolyzed di
Total P ................................. -_
24. 56
24. 97
The dimethyl hydrogen phosphite separated by dis
methyl hydrogen phosphite-the byproduct of the method 75 tillation is continuously condensed and after mixing with
3,089,889
5
fresh feed is continuously recycled to the reactor to
produce additional amounts of dimethyl methane phos
phonate and a complex liquid pynolysis byproduct prin
cipally containing organic phosphorus compounds having
a carbon to phosphorus bond together with minor
amounts of organic phosphorus compounds containing
trivalent and hydrolyzable phosphorus.
6
ous mixture containing dimethyl methane phosphonate,
cooling said mixture to condense a crude product con
taining said phosphonate, and then recovering said phos
phonate by fractional distillation.
5. The method which comprises introducing vaporized
dimethyl hydrogen phosphite into a reaction zone, con
tinuously heating said vapor to a temperature of about
200° C. to about 400° C. to continuously produce a
The pyrolysis reaction is carried out at a temperature
vaporous mixture and as a byproduct a complex liquid
within the range of 200° C. to 400° C., but it is preferred
in practice to operate at a temperature within the range 10 pyrolysis product, continuously cooling said vaporous
mixture to continuously condense a crude liquid product
of 235° C. to `265° C.
containing dimethyl methane phosphonate and unreacted
There is nothing critical about the type or construction
of the reactor so long as the reaction is carried out in the
vapor phase and at a temperature within the above limits.
Moreover, it is not necessary to vaporizc the dimethyl
hydrogen phosphite outside the reactor as it is within the
scope of the invention to adjust the temperature and pres
dimethyl hydrogen phosphite, continuously introducing
said condensate into a still to separate said unreacted
dimethyl hydrogen phosphite from said phosphonate by
fractional distillation, condensing and continuously re
cycling said unreacted dimethyl hydrogen phosphite to
said reaction zone for conversion to further quantities
sure conditions so as to achieve substantially instantane
of dimethyl methane phosphonate and complex liquid
ous vaporization of the above compound as Soon as it
20 pyrolysis byproduct.
enters the reactor.
6. The method which comprises introducing vaporized
Variations in the conditions under which the present
dimethyl
hydrogen phosphite into a reaction zone, con
method is operated, depending upon the nature and sizev
tinuously heating said vapor to a temperature of about
of the equipment and the other factors involved, are con
'235° C. to about 265° C. to continuously produce a va
templated as being within the scope'of the present inven
porous mixture and as a byproduct a complex liquid
25
tion and the invention is not to be construed as being
pyrolysis product, continuously cooling said vaporous
limited to the speciiic conditions or apparatus described
mixture to continuously condense a crude liquid product
herein except as defined in the appended claims.
What We claim is:
l. The method which comprises vaporizing dimethyl
containing dimethyl methane phosphonate and unreacted
dimethyl hydrogen phosphite, continuously introducing
hydrogen phosphite and heating the resulting vapor to a 30 said condensate into a still to separate said unreacted di
temperature of about 200° C. to about 400° C.
2. The method which comprises vaporizing dimethyl
hydrogen phosphite and heating the resulting vapor to a
temperature of about 235° C. to about 265° C.
3. The method of producing dimethyl methane phos
phonate, which comprises vaporizing dimethyl hydrogen
phosphite and heating the resulting vapor to a tempera
ture of about 200° C. to about 400° C. to form a vapor
ous mixture containing dimethyl methane phosphonate,
cooling said mixture to condense a crude product con 40
taining said phosphonate, and then recovering said phos
phonate.
4. The method of producing dimethyl methane phos
phonate, which comprises vaporizing dimethyl hydrogen
methyl hydrogen phosphite from said phosphonate by
fractional distillation, condensing and continuously re
cycling said unreacted dimethyl hydrogen phosphite to
said reaction zone for conversion to further quantities of
dimethyl methane phosphonate and complex liquid pyrol
ysis byproduct.
References Cited in the ñle of this patent
UNITED STATES PATENTS
12,863,900
2,923,729
Beach et -al _____________ _.. Dec. 9, 1958
Hardy ________________ __ Feb. 2, 1960
OTHER REFERENCES
Schrader: British Intelligence Objectives Report No.
phosphite and heating the resulting vapor to a tempera 45 1808, Item 122, pages 19 and 20, released October 4, 1918.
ture of about 235° C. to about 265° C. to form a vapor